1. Field of the Invention
The present invention relates to a valve driving apparatus and an internal combustion engine including the same in a motorcycle, automobile or the like.
2. Description of the Related Art
In an internal combustion engine, combination of a variable phase and cam switching begins to appear recently, and thereafter, a method with use of a three-dimensional cam for making the operation angle and the lift amount continuously variable is proposed. For example, there is a method in which a follow-up mechanism for a change in a contact angle is provided at a top portion of a direct striking type cylinder tappet, and by sliding the three-dimensional cam in an axial direction, the valve lift amount is made continuously variable.
This type of three-dimensional cam is provided extensively with a cam portion inclined in a longitudinal direction (axial direction of a camshaft), and is formed in a shape to continuously change the valve lift amount. In this case, setting is made such that a cam operation angle and lift timing are changed synchronously with cam height so as to have a desired lift curve. By moving such a cam along the camshaft, the lift amount, the operation angle and lift timing of a valve can be controlled to be continuously variable.
By applying such a three-dimensional cam to the intake valve, a throttle valve to form a mixture is removed, and a so-called non-throttle valve engine can be realized. By removing the throttle valve, intake pressure inside an intake port becomes atmospheric pressure or negative pressure close to it with pulsation being averaged, and therefore a lift amount, opening timing and time of the intake valve with respect to, for example, engine speed differ. This is because the conventional engine is developed on the premise that the throttle valve is included, and the intake amount into the cylinder is adjusted with the intake valve, after the flow (pressure) is firstly adjuster with the throttle valve. There is some which change the operation of the intake valve a little among them, but rotation control and output control are performed depending on that the intake passage is throttled with the throttle valve, and if the throttle valve is removed, the control cannot be made at all. In the present invention, the condition of the intake pressure inside the intake port differs, and therefore size and setting of each part totally differ. Even if a component is explained by the same name for convenience of explanation, the role played by it is totally different.
[Patent Document 1]
Japanese Patent Laid-open No. 4-187807
Incidentally, in this type of valve driving apparatus, a slide mechanism of a three-dimensional cam, a mechanism in contact with a three-dimensional cam to advance and retreat the valve and the like are included, and therefore assembling easiness and the like in these mechanisms are required.